Magnetic pickup for stringed musical instruments

ABSTRACT

A magnetic pickup for stringed musical instruments has a balanced coil assembly for each string. Each assembly includes a bar magnet supporting a pair of pole pieces, each pole piece having a separate coil wound thereon. Each coil assembly is provided with an adjustment device for individually balancing the output of each string.

United States Patent 1191 Kosinski 154] MAGNETIC PICKUP FOR STRI'NGED MUSICAL INSTRUMENTS [75] Inventor: Frank .Joseph Kosinski, Hauppauge, NY.

[73] Assignee: Gulf & Western Industries, Inc.,

New York, NY.

[22] Filed: June 22, 19 71 211 App]. No.: 155,528

[52] US. Cl ..84/l.l5, 84/1.l6 [51] Int. Cl. ..Gl0h 3/00 [58] Field ofSearch ..84/1.0l,1.14,1.15,1.16

[56] References Cited UNITED STATES PATENTS 2,892,371 6/1959 Butts ..84/1.l6 2,612,541 9/1952 Armond ..84/1.15 X 2,612,072 9/1952 Armond ..84/1 .15

1 1 Feb. 6, 1973 3,541,219 11/1970 Abair ..84/1.16X 3,571,483 3/1971 Davidson ..84/L16 FOREIGN PATENTS OR APPLlCATIONS 588,178 5/1947 Great Britain ..84/l.15

Primary Examiner-Rlchard B. Wilkinson Assistant Examiner-U. Weldon Attorney-Amster & Rothstein 57 ABSTRACT A magnetic pickup for stringed musical instruments has a balanced coil assembly for each string. Each assembly includes a bar magnet supporting a pair of pole pieces, each pole piece having a separate coil wound thereon. Each coil assembly is provided with an adjustment device for individually balancing the output of each string.

8 Claims, 5 Drawing Figures MAGNETIC PICKUP FOR STRINGED MUSICAL INSTRUMENTS This invention relates to an electromagnetic pickup arrangement for stringed musical instruments, such as electrical guitars, and more particularly relates to a novel arrangement wherein a balanced coil assembly is loudspeaker in a well known manner.

In the past, it has been a general practice for magnetic pickups to employ one coil structure wound around a plurality of pole pieces, each of the pole pieces being in proximity to a different string. In

another arrangement, a separate coil is wound around each pole piece, there being only one pole piece for each string. US. Pat. No. 2,896,491 is an example of a 'magnetic pickup which utilizes the former concept. In

this arrangement, a large coil is wound around all the pole pieces on one side of a magnet with a duplicate coil structure wound around all the pole pieces on the other side of the magnet. In this manner, each of the strings passes over two pole pieces. However, there are several shortcomings with this type of arrangement. First, because of the large coil structure surrounding the six pole pieces, the capacitance of the winding is veryhigh. For example, if the sixpole pieces are spaced 'over a two anda half inch distance, then the coil wound around the six pole pieces would be approximately'five inches long. Since capacitance increases directly with the length of the windingand since there are several thousand of such windings for each coil structure, the capacitance becomes very high and causes a serious reduction in its capability of reproducing all of the higher order harmonics and thereby reduces the quality of. the sound reproduced by the instrument. Second, because one coil structure is wound around a plurality of pole pieces, rather than around each individual pole piece, the magnetic lines of force produced by the pole pieces will only out two sides of the coil structure rather than all four sides. This results in a decreased induced current and therefor adversely affects the sound reproduced by the instrument. This loss is compounded by the fact that the magnetic field is reduced by the square ofthe distance between a pole piece and the coil structure. For example, if the distance from a pole i piece to the coil structure is normally one thirty-second ofan inch and because of the winding configuration, the distance is increased to one-sixteenth of an inch, or

1 doubled, the magnetic field is reduced to one-fourth of its original intensity. As a result, the sensitivity of the magnetic pickup is reduced and, more important, the

low and high level harmonic content of the strings will be lost entirely. Third, in this prior art structural arrangement, there ,is no provision for individually balancing the output current from each of the strings.

" More specifically, there is no provision for individually raising and lowering each pair of pole pieces in order to balance the output from each string. This type of adjustment is desirable when a musician is vibrating some of the strings at a higher amplitude than the others in order to produce varying nodes. If no adjustment is provided for varying the distance between each string and pole piece, this will make some strings sound louder or softer than others when amplified and will result in poor balance of sound. I

As mentioned above, another prior art construction provides only one coil wound around each pole piece, there being only one pole piece and coil for each string of the instrument. In this arrangement, there is also no provision for balancing the output current of each of the strings individually as each of the pole pieces is not separately adjustable with respect to each string. This results in the same problem as above of a poor balance of sound. Moreover, another disadvantage which arises when there is only one pole piece provided for each string is that it allows only fundamental nodes to be reproduced with no capability of reproducing varying nodes.

The magnetic pickups of the prior art are not capable of reproducing a high quality of sound including both lower and higher level harmonics as well as the varying nodes of the vibrating strings which must be reproduced for a full fidelity of reproduction.

It is the general object of this invention to provide a magnetic pickup having an improved mechanical and electrical design in order to provide a much superior reproduced sound. Another object of this invention is to provide a magnetic pickup that'will produce both low and high order harmonics and, further, will produce varying nodes of the vibrating strings as well as the fundamental node.

Briefly, in accordance with the principles of my invention, a magnetic pickup is constructed having a separately adjustable coil assembly for each string of the musical instrument in order to balance the output current of the individual strings. Each coil assembly includes two pole pieces and individually wound coils around each pole piece. This arrangement provides several advantages over the prior art devices. First, having a coil structure separately wound around eachv pole piece substantially reduces the capacitance to a fraction of what it would be when one large coil structure is wound around a plurality of pole pieces. This results in low attenuation of all high order frequencies and thereby results in the most faithful reproduction of all tones and harmonics heretofore obtained. Second, because a separate coil structure is wound around each pole piece, current is induced around all four sides of each of the pole pieces resulting only in negligible losses. This results in maximum sensitivity during induction with a high capability of reproducing both low and high level harmonics. Third, by providing each coil assembly with its own adjustment device, this allows the distance between each pair of pole pieces and its respective string to be varied and thereby balance the output current of the individual string. This avoids the problem of some strings sounding louder or softer than others when vibrated at different amplitudes in order to produce varying nodes.

Further objects, features and advantages of my invention will become apparent upon a consideration of thefollowing detailed description of a presently preferred embodiment when taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a plan view ofa stringed musical instrument having the magnetic pickup of the present invention mounted thereon;

FIG. 2 is an enlarged fragmentary plan view of the magnetic pickup shown in FIG. 1 with parts broken away in horizontal cross-section;

FIG. 3 is an enlarged vertical cross-sectional view of the pickup taken along line 3-3 in FIG. 2 illustrating a representative coil assembly;

FIG. 4 is an enlarged vertical cross-sectional view of the pickup illustrating a coil assembly in a tensioned position; and

FIG. 5 is a schematic view taken along line 5-5 in FIG. 3 illustrating the electrical circuit of the magnetic pickup of the present invention.

Referring now to the specific drawings, there is shown in FIG. 1 a stringed musical instrument embodying the features of the present invention and generally designated by the reference numeral 10. Instrument is an electric guitar which comprises a solid non-vibrating body portion 12 and a neck portion 14 provided with a finger board. The instrument 10 has a plurality of strings 16 that are of magnetic material, such as steel. (Although the number of strings may vary, in the preferred embodiment, there are six). The strings are secured to the body portion 12 by a tail piece 18 and extend over a portion of the body 12 and along the neck portion 14 to a plurality of tuning keys 20 which adjust the tension in the strings to obtain the desired pitch. The strings 16 are held in overlying relation to and are spaced from the body portion 12 by bridge means 22 mounted on the tail piece 18. The metallic strings 16 are also stretched over a magnetic pickup device generally indicated at 24.

As is more clearly illustrated in FIG. 5, the preferred embodiment of the magnetic pickup device 24 comprises six coil assemblies 26, one assembly 26 being provided for each of the six strings of the musical instrument. Fiber shims 28 are placed between adjacent assemblies 26 in order to provide a self-supporting unit when it is placed in the instrument 10. Each coil assembly 26 includes two coils which are connected in series adding, as shown by representative lead 34, and, in addition, all of the coil assemblies are connected in series. The leads from the outermost coil assemblies are the output leads and are connected to a jack 36 (FIG. 1) by means of which the pickup 24 can be electrically connected to an amplifier and loudspeaker in a wellknown manner. I

In FIG. 2, there is shown an enlarged plan view of the magnetic pickup 24 and, the manner in which it is mounted on the body 12 of the instrument 10. The coil assemblies 26 are supported in a case 38 formed of non-magnetic material and having a bottom cover 40 (see FIG. 3). A mounting plate 42 is secured to the body portion 12 of the instrument It) by screws 44 and case 38 is in turn attached to mounting plate 42 by means of mounting and adjust screws 46. Screws 46 are provided so that the entire magnetic pickup 24 may be adjusted as a unit with respect to the strings 16.

As shown in FIGS. 3 and 4, each of the coil assemblies 26 includes a single bar magnet 48, a pair of coils 30, 32, a pair of pole pieces 50, 52 and an adjusting screw 54. The bar magnet 48 is formed of permanent magnetic material and pairs of holes 56 and 58 are formed in each of the bar magnets so that they may receive pole pieces 50, 52. Pole pieces 50, 52 are formed of cylindrical soft iron cores which may be pressed into their respective holes 56 and 58, or otherwise mounted on bar magnets 48, there being a pair of pole pieces for each of the strings 16 of the instrument 10. Each of the pole pieces 50, 52 project through respective insulating bobbins 60, 62, bobbin 60 having a coil 30 wound therearound and bobbin 62 having a coil 32 wound therearound, each coil being wound in a plane parallel to the magnet 48 and the surface of the instrument It). In addition, each of the bar magnets 48 is provided with a tapped hole 64 centrally located between each of the pairs of holes 56, 58. Adjusting screws 54 are threaded into holes 64 with each of the screws 54 having a heavy spring 66 therearound in order to tension the coil assemblies 26. Adjustment of one of the screws 54 will permit its corresponding coil assembly 26 to be raised or lowered in the case 38 in order to balance the output of the individual strings. As shown in FIG. 4, as screw 54 is threaded into bar magnet 48, the entire assembly 26, including magnet 48, pole pieces 50, 52 and coils 30, 32, is brought closer to string 16.

The permanent magnet system created by the permanent magnets 48 and pole pieces 50 and 52 establish north and south poles at the exposed ends of each pair of the pole pieces in proximity to the superimposed metal string 16 of the instrument, and opposite poles are accordingly induced in the metal string. Vibration of the string causes it to move over the ends of the pole pieces creating a variation in the magnetic field through the coils 30, 32 in a well-known fashion. In the preferred embodiment, each pole piece 50 has a north pole at its upper end and a variation in the strength of the magnetic field (by plucking of the respective strings) will tend to create a current in the coil 30 in the direction indicated by the arrow 68 and a concurrent vibration of a string 16 over the pole piece 52 will tend to induce a current in the coil 32 in the same direction, as indicated by the arrow 70. The currents in the two coils are thus added together and this resultant current is added to the currents produced in the other coil assemblies 26 to provide a strong signal in response to vibration of the strings 16. A maximum number of turns are provided for each of the coils 30, 32 in order to achieve an output equivalent to that which is derived from a rhythm and blues guitar.

From the foregoing, it will be appreciated that there is provided in accordance with the present invention, a magnetic pickup for a stringed musical instrument having an individually adjustable coil assembly for each string which allows a balanced output current to be produced for each string. Further, because a coil structure is separately wound around each pole piece, the capacitance produced remains low and allows all high order harmonics to be produced. Also, as a result of providing separately wound coils, the magnetic lines of force from each of the pole pieces cut through all sides of the coil structure, resulting in an increased induced current, thereby increasing the sensitivity of the pickup and, more important, increasing the capability of reproducing both the low and high level harmonic con- Y tent of the strings. Moreover, due to the fact that there are two pole pieces provided for each string of the stances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What is claimed is:

l. A magnetic pickup for a stringed musical instrument comprising a plurality of coil assemblies, each of said coil assemblies including a magnet, each of said coil assemblies further including a plurality of pole pieces supported on said magnet, each of said coil assemblies also including a plurality of induction coils equal in number to the plurality of pole pieces, each of said plurality of induction coils being separately wound around one of said pole pieces with the coils being electrically connected in series, means for connecting the outputs of said coil assemblies and means for supporting said plurality of coil assemblies on a stringed musical instrument with each string of the instrument passing over a different one of said coil assemblies.

2. A pickup according to claim 1 further including means for individual adjustment of each of said coil assemblies so that each of the coil assemblies may be individually raised or lowered to balance the output of each string.

3. A pickup according to claim 1 wherein said magnetic pickup is adjustably mounted on said instrument.

4. A pickup according to claim 1 further comprising fiber shims located between adjacent coil assemblies to align said coil assemblies so as to provide a self-supporting pickup.

5. A pickup according to claim 2 wherein said adjustment means includes spring-biasing means in order to separately tension each of said coil assemblies.

6. A pickup according to claim 1 wherein each of said pole pieces are formed of magnetizable material and are mounted in holes formed in said magnets.

7. A pickup according to claim 6 wherein an insulating bobbin is mounted on each pole piece, with each bobbin supporting one of said separately wound coils thereon.

8. A pickup according to claim 1 wherein said plurality of pole pieces includes a first and second pole piece mounted on opposite ends of said magnet. 

1. A magnetic pickup for a stringed musical instrument comprising a plurality of coil assemblies, each of said coil assemblies including a magnet, each of said coil assemblies further including a plurality of pole pieces supported on said magnet, each of said coil assemblies also including a plurality of induction coils equal in number to the plurality of pole pieces, each of said plurality of induction coils being separately wound around one of said pole pieces with the coils being electrically connected in series, means for connecting the outputs of said coil assemblies and means for supporting said plurality of coil assemblies on a stringed musical instrument with each string of the instrument passing over a different one of said coil assemblies.
 1. A magnetic pickup for a stringed musical instrument comprising a plurality of coil assemblies, each of said coil assemblies including a magnet, each of said coil assemblies further including a plurality of pole pieces supported on said magnet, each of said coil assemblies also including a plurality of induction coils equal in number to the plurality of pole pieces, each of said plurality of induction coils being separately wound around one of said pole pieces with the coils being electrically connected in series, means for connecting the outputs of said coil assemblies and means for supporting said plurality of coil assemblies on a stringed musical instrument with each string of the instrument passing over a different one of said coil assemblies.
 2. A pickup according to claim 1 further including means for individual adjustment of each of said coil assemblies so that each of the coil assemblies may be individually raised or lowered to balance the output of each string.
 3. A pickup according to claim 1 wherein said magnetic pickup is adjustably mounted on said instrument.
 4. A pickup according to claim 1 further comprising fiber shims located between adjacent coil assemblies to align said coil assemblies so as to provide a self-supporting pickup.
 5. A pickup according to claim 2 wherein said adjustment means includes spring-biasing means in order to separately tension each of said coil assemblies.
 6. A pickup according to claim 1 wherein each of said pole pieces are formed of magnetizable material and are mounted in holes formed in said magnets.
 7. A pickup according to claim 6 wherein an insulating bobbin is mounted on each pole piece, with each bobbin supporting one of said separately wound coils thereon. 